A rotary compression molding machine that can mass-produce tablets has been typically used in the pharmaceutical field in recent years. The rotary compression molding machine includes a rotary die table having die bores, and upper punches and lower punches that are retained respectively above and below the die bores so as to be slidable upward and downward. The rotary compression molding machine causes the die table and the punches to horizontally rotate together and compression molds a powdery material filled in the die bores when the upper punches and the lower punches pass between upper and lower rolls (see Japanese Unexamined Patent Publications JP 2009-095855 A, JP 2011-218432 A, and JP 2011-255397 A, for example).
A small rotary compression molding machine is often used at a research and development stage. Such a compression molding machine is not required to have very high production performance at the research and development stage. The compression molding machine is required instead to have versatility and multifunctionality so as to produce various types of tablets such as double layer tablets, triple layer tablets, and dry-coated tablets.
Providing multifunctionality even to a small rotary compression molding machine causes a heavy burden in terms of cost.
Considered accordingly was a configuration of a single stroke compression molding machine satisfying the above requirements.
Japanese Unexamined Patent Publication JP 2013-043212 A discloses a configuration for production of a double layer molded product, in which a first powder supplier moves to a position above a die, supplies the die with a powder for a first layer, and moves from the position above the die. A second powder supplier subsequently moves to the position above the die, supplies the die with a powder for a second layer, and moves from the position above the die. An upper punch and a lower punch then compression mold the powders in the die.
In the configuration disclosed in JP 2013-043212 A, the powder left on a die table by the first powder supplier and the powder left on the die table by the second powder supplier are mixed together to cause contamination by these powders.
JP 2009-095855 A discloses a rotary compression molding machine configured to produce a triple layer tablet supplies a die bore with powders for second and third layers and sucks to remove the powders out of the die bore using a dust collector before the powders are compression molded, in order to eject only a compression molded first layer portion or the like at an ordinary molded product ejecting position as a sample.
The technique disclosed in JP 2009-095855 A is sucking to remove the powders once fed into the die bore out of the die bore before the powders are compression molded. This technique fails to remove an unnecessary powder remaining on a rotating die table so as to prevent contamination by the powders.
JP 2011-218432 A discloses a method of removing an unnecessary powdery material remaining on a rotating die table of a rotary compression molding machine. Specifically, a cleaning powdery material is supplied on the die table and is agitated by an agitating blade of a cleaning device to clean the rotating die table, and an unnecessary powdery material as well as the cleaning powdery material are removed by a dust collecting mechanism.
The cleaning device described in JP 2011-218432 A cleans the rotating die table after a completed molded product is ejected from a die bore. The cleaning device does not clean the rotating die table during production of the molded product, particularly, after a first feeder fills a powdery material for a first layer and before a second feeder fills a powdery material for a second layer. The cleaning device thus fails to prevent contamination by these powdery materials.
JP 2011-255397 A discloses a rotary compression molding apparatus configured to produce a dry-coated tablet as a molded product having a core (an internal core or a core tablet) buried therein. Specifically, a transfer disc of a core supplier is rotated in synchronization with rotation of a rotating die table by a servo motor, and the core tablet is supplied from the transfer disc into a die bore in the rotating die table.
However, a single stroke compression molding machine does not include any rotating die table, and does not need to rotate a rotating die table having die bores in synchronization with a transfer disc configured to supply each of the die bores with a core. The mechanism disclosed in JP 2011-255397 A is not applicable to the single stroke compression molding machine.